Method of gluing wet veneers to backings and drying them



June 28, 1932.

A. ELMENDORF METHOD OF GLUING WET VENEERS TO BACKINGS AND DRYING THEMFiled May 16, 1931 Patented June 28, 1932 UNITED; STATES PATENT OFFICE ARMIN ELMENDORF, OF CHICAGO, ILLINOIS ASSIGNOR TO THE FLEXW 'OODCOIMIPANY,

A CORPORATION OF DELAWARE METHOD OF GLUING WET VENEEBS TO BACICNGS ANDDRYING THEM Application filed May 16,1931. Serial No. 537,804, I

.In my prior Patent, No. 1,714,859, I have disclosed a process forgluing very thin wood veneer to a flexible backing and drying thecomposite sheet thus formed. In the specific example described in thepatent to explain my invention, the backing and the veneer are in theform of rolls,the backing and the veneer being progressively broughtinto contact with each other by being fed between .0 pressure rollers.However, much of" the veneer employed in the commercial manufacture ofcomposite sheets in accordance with the invention of said patent is inflat sheet form, and the present invention has for its ob- ,5 ject toprovide a simple and novel process for producing'and drying thiscomposite material from flat sheet veneer,by gluing the entire area ofeach piece of veneer to the backing at one operation.

: Wood veneer, in drying from its original wet or green state, shrinksto a considerable degree across the grain. Therefore, when a sheet ofwet or green veneer is glued to a paper or other flexible backing, itwill shrink i "pn drying, unless restrained from doing so,

and will cause the backing to shorten by curling; so that the compositesheet will not lie flat. If the composite sheet is held taut while theveneer is drying, the veneer cannot de :0' crease in its dimensiontransversely of the grain but, if thin enough, it will stretch sufficiently to compensate for the natural shrink-' age and thus permit theflexible backing to remain flat. Since the specific-adaptation of Lmyprocessillustratedin my aforesaid patent is a continuous one, the dryingmust be done quickly and, therefore, external heat is applied for thispurpose. Viewed in one of its aspects, my invention may be'said to havefor its object to produce the flat flexible, dry,-comp'osite sheets in asimple manner without the application of external heat.

In its broadest aspect, my invention may, however,be regarded as havingfor its object to provide an extremely simple, economical, and efficientprocess of gluing thin wood veneers to flexible backings so as toproduce compositesheets that are dry and flat.

In carrying out the present invention, I simply assemble wet veneer anda backing faced with dry water-soluble glue and press the two togetherand then hold them tightly between dry water absorbent pads or boardssufiiciently massive to enable them to take up the excess moisture fromthe veneer. In order to save one operation, the initial pressingtogether of the veneers and backings is preferably done" while they liebetween the pads or boards which subsequently dry them.

These pads may be ordinary sheets of fiber board or pulp board of thetype that willto the square inch to one hundred pounds to the squareinch having been successively employed. The pressure on the stack needbemaintained only for a minute or two, in which time sufficient moisturewill pass from the wet veneer to the dry glue to render the latter tackyand cause the veneers to adhere to the backings.

The stack is then removed from the press and is allowed to stand for aconsiderable period of time, say from 'four to twenty hours, dependingupon the thickness of the veneers and their original moisture content.Ordinarily a caul will be. placed underneath and another on top'of thestack, in which case even the uppermostcomposite sheets will be heldunder 'suflicient pressure during the long a drying period.

The moisture content of the veneers will ordinarily not bereduced, whilethey remain inthe press,to a point at which shrinkage begins. However,because the veneers have already beenfiattened against and caused toadhere to the backings, the clamping action of the absorbent boards orpads on the composite sheets constrains the veneers against shrinking ordeveloping cusps during the subsequent drying.

l Q moisture on exposure to the air. The veneer may contain 100% ofmoisture initially and yet, at the end of the process, it need notcontain more than 6% or 8% of moisture, if that low a moisture contentbe desired.

The absorbent pads must, of course, be dried from time to time. They maybe placed in a drying chamber in such positions that air may reach allparts of the broad surfaces thereof, and be dried in about half an hourby blowing dry, warm air across the same. The drying of the pads orboards, therefore, requires only a small fraction of the time consumedin my new process of gluing and drying the'composite panels.

The various features of novelty whereby my invention is characterizedwill hereinafter be pointed out with particularity in the claims; but,for a full understanding of my invention and of its objects andadvantages, reference may be had to the following detailed descriptiontaken in connection withthe accompanying drawing, wherein:

Figure 1 is an edge View of two absorbent pads or boards separated fromeach other and having interposed between the same a backing sheet and aplurality of pieces of wood veneer, the view being diagrammatic andrepresenting each element above the lower board as being in the act ofdescending toward the next lowermost element with which it is to engage;Fig. 2 is a perspective view, on a greatly exaggerated scale, showing afragment of the glue faced backing and an overlying fragment of woodveneer to be glued to the backing; Fig. 3 is a side view of a completedstack in which numerous composite sheets are undergoing the gluing anddrying process; and Fig. 4 is a vertical section through a fragment ofthe stack at one side thereof, the thicknesses of the backings, gluelayers and veneers being greatly exaggerated.

Referring to Fig. 2 of the drawing, 1 represents a flexible sheet ofpaper fabric having one broad face covered with a thin layer 2 of'drywater-soluble glue. Overlying the glue is a layer of thin wood'veneerwhich ordinarily will be from 1/40 of an inch to 1/100 of aninchinthickness, although my process may be employed'to advantage evenwith somewhat thicker veneers. If the ve neer contains sufficientmoisture, as it will if still in a green state or if it is dampenedafter it has become dry, sufiicient moisture will pass from the veneerto the glue to render the latter tacky where the veneer and the backingare pressed together, and the veneer will be firmly united to theflexible backing sheet. It then only remains necessary to remove fromthe composite sheet the moisture in excess of that which it should haveas a commercial product. The veneer comes in variouswidths, as Well asin various lengths. It is not necessary to employ a backing sheet of theexact size of each sheet of veneer, but a. plurality of pieces of veneermay be laid upon the same large backing sheet. Thus, in Fig. 1, I haveshown a large flexible backing sheet 1 which is laid upon a massive pador board 4 of water-absorbent material. This sheet, as heretoforeexplained, is faced with glue, the glue being on the upper side. On theflexible sheet are laid one or more pieces of wood veneer, three suchpieces being shown in Fig. 1. Then, on top of the veneer, I lay a secondwater-absorbent pad or board 5. Another backing sheet and one or morepieces of veneer are then laid upon the pad or board 5, as shown in Fig.4, and a third absorbent pad or boardis laid on top of this secondcomposite sheet. In this way, an entire stack, indicated as a whole bythe letter A in Fig. 3, is built up. Each backing sheet, with itsoverlying veneer, is very thin so that the completed stack will have theappearance of a solid laminated block. It is not necessary that theveneer cover the entire surface of the corresponding backing sheet,notwithstanding the fact that the overlying absorbent pad or board willcome in contact with those portions of the glue covered face of thebacking that are left exposed by the veneer, because the glue is dry, asare also the absorbent panels and, therefore, the panels will not adhereto the glue.

After the stack has been completed, it is put under pressure in asuitable power press so as to flatten the veneers and bring them intointimate contact with their respective backings. In a. very short timeenough of the moisture in the wet veneer passes into the glue andsoftens it sufliciently to unite the veneers to their backings; some oftne moisture also being taken up by the pads or boards. Upon removal ofthe stack from the press moisture will continue to be absorbed by thepads or boards at such a rate that, in from four to twenty hours, thecomposite sheets will have become dry. The stack is then taken down, alayer at a time, and the absorbent pads are placed in a drying chamberso as to remove therefrom the moisture that was taken up thereby duringthe process of gluing and drying the composite sheets, and place thepads in condition for further use. So far as the composite sheets areconcerned, the gluing and drying thereof is complete at the time oftheir removal from the stacks.

It will thus be seen that I have produced a simple, novel and eiiicientmethod of gluing thin wet veneers to flexible backings and drying them,the method requiring no skilled labor and no heating of the productduring the process of its manufacture. It will also Consequently, myinvention is not only simple and novel, but it is very inexpensive.

It should be noted that, while my invention is particularly adapted tothe gluing and drying. of wood veneers so thin that wet glue would ormight strike through the same, it is also useful in gluing thickerveneers.

While I have illustrated and described with particularity only a singlepreferred manner of my invention, I do not desire to be limited to theexact structural details or the exact steps thus illustrated anddescribed; but intend to cover all forms, arrangements and methods,including any in which a composite sheet including veneer still wet andglue in a viscous state is held tightly between absorbent pads, whichcome within the definitions of my invention constituting the appendedclaims.

I claim: I

1. The method of gluing wet thin wood veneer to a flexible'backing andat the same time drying the veneer, which consists in pressing'acomposite sheet, composed of a sheet of such veneer and a backing sheetwith viscous glue interposed between them, between massive pads ofwater-absorbent material under suflicient pressure to hold the veneeragainst shrinking, and allowing the composite sheet to remain betweenthe pads until the reater part of the moisture therein has been a sorbedby the pads.

2. The method of gluing wet thin wood veneer to a flexible backing andat the same time drying the teneer, which consists in assembling a sheetof veneer and a backing sheet with glue interposed between them,pressing the veneer and the backing together so as tounite them into acomposite sheet and holding the composite sheet firmly between massivepads of water-absorbent material, and allowing the composite sheet toremain between the pads until the greater part of the moisture thereinhas been absorbed by the pads.

3. The method of gluing wet thin wood veneer to a flexible backing andat the same time drying the veneer, which consists in providing abacking with a thin coating of water-soluble dry glue, laying on thecoating a wet sheet of thin wood veneer, forcing the veneer and thebacking together under suflicient pressure to bring them into intimatecontact with each other and for a sufficient time to cause the glue tobecome tacky and unite the veneer and the backing, holding the compositesheet thus produced between massive pads of water-absorbent ma terial,and allowing the composite sheet to remain between the pads until thefree moisture and a part of the hygroscopic moisture of such labor as isin the wood has been absorbedby the pads.

4. The method of gluing wet thin wood veneer to a flexible backing andat the same time drying the veneer, Which consists in assembling a sheetof veneer and abacking sheet with glue interposed between them, placingthe composite sheet between massive pads of water-absorbent vmaterialunder suf ficient pressure to bring all parts of the veneer int'ointimate contact with the backing, and allowing the composite sheet toremain between the pads until all of the free moisture and a part of thehygroscopic moisture therein has been absorbed by the pads.

5. The method of gluing wet thin wood veneer to a flexible backing andat the same time drying the veneer,'whiclr;;;consists in providing abacking with a thin coating of water-soluble dry glue, laying on thecoating a wet sheet of thin wood veneer, pressing the composite sheetbetween massive pads of water-absorbent material, and allowing thecomposite sheet to remain between the pads until the wood and thebacking have become united and the greater part of the moisture in thewood has been absorbed by the pads.

6. The method of gluing wet wood veneers to flexible backings and at thesame time drying the veneers, which consists in forming a stack of thickboards of water-absorbent material alternating with composite sheetscomposed of wet thin wood veneers laid upon flexiblebackings with glueinter posedbetween the veneers and the backings,

compressing the stack to unite the veneers to the backings, and allowingthe stack to stand until'all the free moisture and some of thehygroscopic moisture in the veneers has been absorbed by the absorbentpanels.

7. The method of gluing wet wood veneers to flexible backings and at thesame time drying the veneers, which consists vin forming a stack ofthick boards of water-absorbent material alternating with compositesheets composed of wet thin wood veneers laid upon flexible backingswith dry water-soluble glue' interposed between the veneers and thebackings, compressing the stack to unite the ve-' ings, compressing thestack to unite the veneers to the backings, relieving the pressure onthe stack and allowing the stackj tofstand y until all of the freemoisture and a partpf the hygroscopic moisture in the veneers has beenabsorbed by the absorbent boards, taking down the stack and then dryingthe absorbent boards to place them in condition to 5 be used in anothergluing and drying operation.

In testimony whereof, I sign this specification.

ARMI N ELMENDORF.

